Various apparatus are employed for arranging sheet material in a package suitable for use or sale in commerce. One such apparatus, useful for describing the teachings of the present invention, is a mail piece inserter system employed in the fabrication of high volume mail communications, e.g., mass mailings. Such mailpiece inserter systems are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mail communications where the contents of each mailpiece are directed to a particular addressee. Also, other organizations, such as direct mailers, use mailpiece inserters for producing mass mailings where the contents of each mail piece are substantially identical with respect to each addressee. Examples of inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. located in Stamford, Conn., USA.
In many respects, a typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (i.e., a web of paper stock, enclosures, and envelopes) enter the mailpiece inserter as inputs. Various modules or workstations in the mailpiece inserter work cooperatively to process the sheets until a finished mail piece is produced. The precise configuration of each inserter system depends upon the needs of each customer or installation.
Typically, mailpiece inserters prepare mail pieces by arranging preprinted sheets of material into a collation, i.e., the content material of the mail piece, on a transport deck. The collation of preprinted sheets may continue to a chassis module where additional sheets or inserts may be added to a targeted audience of mail piece recipients. From the chassis module the fully developed collation may continue to a stitcher module where the sheet material may be stitched, stapled or otherwise bound. Subsequently, the bound collation is placed into a mailpiece envelope and conveyed to yet other stations for further processing. That is, the envelopes may be closed, sealed, weighed, sorted and stacked. Additionally, the inserter may include a postage meter for applying postage indicia based upon the weight and/or size of the mail piece.
FIGS. 1a-1c show the relevant components of a prior art chassis module/station 200 of an inserter system. The figures show the chassis module 200 conveying a sheet material 212 along a transport deck 214 (omitted from FIG. 1a to reveal underlying components). The transport deck 214 includes a drive mechanism 216 for displacing the sheet material 212 as it slides over the transport deck 214. In FIG. 1c, the transport deck 214 includes a low friction surface 214S having a pair of parallel grooves or slots 214G formed therein. Riding in the grooves or through the slots 214G are fingers 216F which extend orthogonally from the surface 214S of the deck 214.
Referring to FIGS. 1a-1c, the fingers 216F are driven by a belt or chain 218C1 which, in turn, wraps around a drive sprocket or gear 218G. Furthermore, the fingers 216F1 are spaced in equal length increments while the fingers 216F2, of adjacent chains 218C1, 218C2 are substantially aligned, i.e., laterally across the transport deck 214. As such, a substantially rectangular region or pocket is established between the fingers 216F1, 216F2.
Above the transport deck 214 are one or more feeder mechanisms 220A, 220B (two are shown for illustration purposes) which are capable of feeding inserts 222, i.e., sheet material, to the transport deck 214. The inserts 222 may be laid to build a collation 212 or may be added to the sheet material 212 (i.e., a partial collation) initiated upstream of the transport deck 214. A controller (not shown) issues command signals to the feeder mechanisms 220A. 220B to appropriately time the feed sequence such that the inserts 222 are laid in the rectangular region 224 between the fingers 216F1, 216F2. More specifically, as each pair of lateral fingers 216F1, 216F2 is driven within the grooves or slots 214G, one edge of the sheet material 212 is engaged to slide the collation 212 along the transport deck 214. As the sheet material 212 passes below the feeding mechanisms 220A, 220B, other sheets or inserts 222 are added. At the end of the transport deck 214, the fingers 216F1, 216F2 drop beneath the transport deck 214 such that the collation (i.e., the combination of the sheet material and inserts 222) may proceed to subsequent processing stations.
While the drive mechanism 216 of the prior art provides rapid transport of collated sheet material 212, 222, the stacked sheets/inserts 222 fed by the feeding mechanisms 220A, 220B can become misaligned in the rectangular space or pocket 124 provided between the fingers 216F1, 216F2. That is, inasmuch as the pocket 224 is oversized to accept the sheets or inserts 222, the inserts 222 can become misaligned due to a lack of positive registration surfaces on all sides of the collation 212, 222.
Various mechanisms are employed to vary the pocket size, i.e., sometimes referred to as the “pitch”, between the chassis fingers. The ability to change pitch not only enables greater efficiency, i.e., a greater number of pockets for inserts, but also minimizes the misalignment of inserts being laid on a collation. Notwithstanding the ability to minimize pocket size, it will be appreciated that without positive restraint on all free edges of the collation, individual sheets or inserts will be misaligned. Consequently, prior art inserters commonly employ complex registration mechanisms or jogging devices to align the free edges of a collation. For example, inserters may employ a series of swing arms which pivot onto the transport deck, i.e., into the conveyance path of the collation. The swing arms engage and align the leading edge of a collation, i.e., the edge opposite the fingers. While the swing arms effectively maintain alignment of the collation, the mechanical complexity associated with the pivoting mechanism is a regular source of maintenance, jamming and/or failure.
In the absence of such swing arms, an inserter may employ other jogging mechanisms to align the edges of the collation. Such jogging mechanisms often employ a complex arrangement of rotating cams/discs which tap or “jog” each edge by a predetermined displacement. While such rotating cam mechanisms are useful for aligning relatively thin collations, e.g., less than fifty (50) sheets of material, thick collations can be more difficult to align due to the weight of the stacked sheets. That is, inasmuch as the weight increases the frictional forces developed between individual sheets of material, i.e., especially the lowermost sheets of the collation, it is more difficult to effect the requisite movement between sheets to align the edges of the collation. As a consequence, the edges of misaligned sheets can be damaged or torn by the motion/action of such prior art jogging mechanisms.
Additionally, many mailpiece inserters employ mechanisms, e.g., a stitcher or a stapler, to bind the collations as they travel along the transport and alignment system. These binding mechanisms must be manually adjusted depending upon the anticipated thickness of a collation within a particular mail run. That is, the size of the stitch or staple must be anticipated to penetrate and bind the collation. This operation requires significant operator intervention and does not accommodate consecutive collations which vary in thickness. With respect to the latter, stitchers/staplers of the prior art cannot bind collations which vary in thickness from one collation having a thickness of, for example, one-half inch (½″), to a subsequent or consecutive collation having a thickness of, for example, three-quarter inches within the same mail run. This is due to the fixed or constant thickness staples used in, or stitches produced by, the stitcher/stapler. While some small variation may be accommodated by the same size stitch or staple, stitcher/staplers of the prior art are generally limited to binding constant thickness collations.
In view of the foregoing it will be appreciated that transport and alignment systems, especially those which employ binding mechanisms along the feed path, are limited in terms of their throughput or processing speed. That is, in view of the time required to jog, align, bind and transport collations along the feed path, these systems can only process a fixed number of collations per unit time.
A need, therefore, exists for a system and method for producing multi-sheet collations which improves reliability, increases throughput, and minimizes mechanical complexity.